Abstract: A novel tolan compound of the formula (I): wherein A is C1-10 alkyl, C1-10 alkoxy, cyclohexyl substituted by C1-10 alkyl at 4 position, cyclohexyl substituted by C1-10 alkoxy group at 4 position or a group of the formula: wherein Y is hydrogen or halogen and Z is C1-10 alkyl or halogen; B is a single bond or —CO—O— or —O—CO—; D is hydrogen, C1-10 alkyl, cyclohexyl substituted by C1-10 alkyl at 4 position; and Z represents a hydrogen atom or a halogen atom. The tolan compound can increase the N-I point, decrease the viscosity, and increase the double refractive index of a liquid crystal composition without affecting the viscosity and threshold voltage Vth, and is mutually soluble with various other liquid crystal compounds, so that the compound can be used as a constituent of a liquid crystal composition in combination with these other liquid crystal materials to improve the properties of the composition.

Abstract: A novel tolan compound of the formula (I): ##STR1## wherein A is C.sub.1-10 alkyl, C.sub.1-10 alkoxy, cyclohexyl substituted by C.sub.1-10 alkyl at 4 position, cyclohexyl substituted by C.sub.1-10 alkoxy group at 4 position or a group of the formula: ##STR2## wherein Y is hydrogen or halogen and Z is C.sub.1-10 alkyl or halogen; B is a single bond or --CO--O-- or --O--CO--; D is hydrogen, C.sub.1-10 alkyl, cyclohexyl substituted by C.sub.1-10 alkyl at 4 position; and Z represents a hydrogen atom or a halogen atom. The tolan compound can increase the N-I point, decrease the viscosity, and increase the double refractive index of a liquid crystal composition without affecting the viscosity and threshold voltage Vth, and is mutually soluble with various other liquid crystal compounds, so that the compound can be used as a constituent of a liquid crystal composition in combination with these other liquid crystal materials to improve the properties of the composition.

Abstract: A novel tolan compound of the formula (I): ##STR1## wherein A is a substituted or unsubstituted cyclohexyl or phenyl group; B is --CO--O-- or --O--CO--; X is a hydrogen atom, a halogen atom, a cyano group, a C.sub.1 -C.sub.10 alkyl group, or a C.sub.1 -C.sub.10 alkoxy group; Y is a hydrogen atom or a halogen atom; and m and n are an integer of 0 or 1, provided that m+n=0 or 1. The tolan compound can raise the N-I point and increase the double refractive index (.DELTA.n) of liquid crystal compositions. The liquid crystal composition containing this tolan compound has excellent characteristics as a liquid crystal material, and the liquid crystal display device using this liquid crystal composition has a wide temperature range and a wide visible angle and can be operated at a low driving voltage.